they did need fox and sony to remind them though with xmen, mib and spiderman, even then they murdered their first attempt to bring back superman and failed miserably at doing the green lantern. People like to shit on fox and sony now but they were the ones to get things really rolling in the early 00's.
Before that it was really only supes and batman that had been given the blockbuster treatment and it took 11 years after the success of the first superman movie for Batman to happen.
You could try to argue Dick Tracy and TMNT but these were low budget efforts, costing less to make than the original superman unadjusted for inflation and in the turtles case less than half.
There were other attempts in their like judge dread but it followed the unsuccessful formula of lets make a movie into a comic book rather than the successful adapt a comic book into a film. Ironically though when they eventually did do a better adaptation of dredd it bombed more than the original.
Even the first X men movie was a much lower budget attempt compared to its contemporary films. The Mystery Men movie cost almost as much.
The floodgates were well and truly open as far as comic book movies and it took WB a long time after that to get back in the saddle with very mixed results.
If they really knew about superheros making money they wouldn't have lost money making superman returns and green lantern. If they really new about this cash cow there wouldn't be the situation where a mainstream ant man movie is likey to be in theaters before we even hear about a flash or wonder woman movie.